CVM has been applied to measure the value of non-market goods including natural environment. It has been known that measuring values by CVM tends to involve a number of biases. Consequently the NOAA's guidelines were proposed for measuring values without biases by CVM. However, the validity of the guidelines has not been clearly tested. In the present study, we replicated the CVM survey designed according to the guidelines by Kuriyama et al. for measuring values of natural environment in Yakushima-Island, and analyzed cognitive decision making processes based on a verbal-protocol method. The analysis indicated that it is not easy at all to measure value without any biases by CVM designed according to the NOAA's guidelines.